The invention relates to a method for determining a position point of a movable element, particularly of a window or of a roof of a motor vehicle which can be advanced into at least one elastic receptacle by means of a drive.
Movable elements, in particular windows or roofs, are used, for example, in motor vehicles as electric activated windows or as electric activated sunroofs. The electric closing devices of the windows or roofs which are provided for this purpose have to ensure both a trapping protection, in order to largely prevent injury to the user as a result of trapping body parts, and move the movable element safely into an elastic receptacle, with the result that the movable element, together with the elastic receptacle, seals off the passenger compartment of the vehicle from external weather influences.
EP 0 883 724 B1 describes an adjustment drive having trapping protection for movable elements, in which the rotational speed and/or the power of the adjustment drive is lowered according to a predefined mathematical function in a specific adjustment range within a predefined position region before the movable element advances into an elastic receptacle, with the result that the movable element advances into the elastic receptacle at a minimum speed. The position for the stopping of the movable element is determined here from the indirectly measured position thereof.
The position for the stopping of the movable element is subject to wear, voltage fluctuations in the on-board power system of the vehicle or climatic influences on the closing device, with the result that the desired stopping position often does not correspond to the stopping position which is adopted. In order to avoid this, EP 0 697 305 A1 proposes an adjustment drive for windows and sunroofs having a control system which determines the position of the movable element from the power drain of the motor. Locking of the electric motor of the drive is inferred from an increase in the current profile, and stopping of the drive is initiated. This procedure leads to a situation in which the movable element advances into the elastic element in an unbraked fashion and gives rise to clearly audible noise in this way.